Optimization of pressure oxidation process to prepare sodium pyroantimonate from sodium thioantimonite solution

The pressure oxidation process to prepare sodium pyroantimonate from sodium thioantimonite solution was optimized. The results indicate that increasing reaction temperature, oxygen partial pressure and stirring speed can significantly accelerate the oxidation precipitation rate of Sb. A decrease in Sb3 + concentration is beneficial for shortening the reaction time. The NaOH concentration has no significant effect on the oxidation velocity but plays an important role in the quality of sodium pyroantimonate. An increase in stirring speed and oxygen partial pressure result in the formation of a red precipitation in the solution with 12.5 g/L of NaOH, while the desired sodium pyroantimonate can be produced with a NaOH concentration of 30.0 g/L. The XRD and SEM-EDS analysis confirm that the red precipitate is composed of NaSb(OH)6 and Na6Sb4S9.